Asthma Drugs: Too Much of a Good Thing?

Aug. 15, 2003 -- New research may explain a puzzling paradox of asthma treatment -- why the medications used to open constricted airways during asthma attacks ultimately make some patients sicker.

The findings could lead to new drugs to prevent the disease-worsening side effects of asthma treatment with quick-acting inhalers, says study researcher Stephen Liggett, MD, of the University of Cincinnati College of Medicine.

"We have known that asthma symptoms tend to be exacerbated for many people treated with these medications," Liggett tells WebMD. "There is a lot of epidemiological evidence, but it doesn't tell us why this is happening."

In an attempt to answer this question, Liggett and colleagues studied airway function in genetically altered mice. They found that mice altered to mimic long-term exposure to these quick-acting asthma medications -- called beta-agonists -- had higher levels of an enzyme known as phospholipase C-beta (PLC-beta).

The quick-acting asthma inhalers open the airways during an asthma attack, but this enzyme acts to close it down, Liggett says.

Liggett and colleagues suggest that drugs targeting this enzyme could prevent the harmful side effects of quick-acting asthma inhalers. Their research is published in the Aug. 15 issue of the Journal of Clinical Investigation.

People with asthma should also be aware of the potential for overuse of quick-acting asthma inhalers -- a sign of uncontrolled asthma. If you need to use your quick-acting inhalers more than twice a week, talk to your doctor about increasing the medication you take to prevent asthma attacks as opposed to treating them once they've begun.

Stephanie Shore, PhD, who wrote an editorial accompanying the study, tells WebMD that asthma patients should not hesitate to use quick-acting inhalers during asthma attacks, but she adds that the evidence is mounting that the drugs should not be used routinely in the absence of attacks. A recent study by the National Institutes of Health suggested that patients who used a widely prescribed rescue inhaler for asthma attack fared better than those who used it routinely throughout the day.

Studies also indicate that certain patients are more likely to have harmful treatment reactions than others. Researchers have identified a particular genetic trait that seems to predispose patients to this potential reaction from quick-acting asthma treatments.

"The implication is that taking these medications does not pose a problem for one group of patients, but for the subtype with this genetic predisposition they do," Shore says. "People with asthma need to be on [rescue medication], but the hope is that we can find a way to give them without worsening the disease."